The present invention relates to a manganese-chromium steel to be used for construction parts, preferably tubes or pipes, which will be operated at very low temperature (cryogenics).
Ferritic nickel steels, having up to 9% nickel are used at low temperatures, but only above -190.degree. C. Austenitic chromium nickel steel of the type X 12 CrNi 18 9 is used at lower temperatures. Also, aluminum or austenitic manganese steel of the type X40 MnCr with 4% chromium added can be used at lowest temperature.
Particularly the material known under the designation X40MnCr 22 has still adequate and desirable ductility at low temperatures. However, all these known materials have a relatively large coefficient of thermal expansion. Thus, as parts made of any such material are cooled down to operating temperature, their dimensions change significantly. Considering for example pipe lines, they incur considerable changes in length dimensions and extensive and expensive steps must be taken e.g. for length compensation at interconnections only short distances apart. Moreover, steel with a high nickel content is quite expensive.